In a some cases a number of specific complications can occur:

Arrhythmias

Arrhythmias, irregularities of the heart beat, are a common complication. Symptoms such as palpitation may occur, but not often. Exercise testing or Holter monitoring may detect them. The arrhythmias called ventricular tachycardia (arising from the ventricles) or atrial fibrillation (described below) are particularly important and may require treatment. Atrial Fibrillation, the normal regular rhythm of the heart beat is lost and replaced by an irregular rhythm which may be episodic or persistent. The loss of normal atrial (the top of the heart) contraction produces a risk of clot formation in the atria. Anticoagulants and drugs to slow the heart rate are required.

Endocarditis

This is an infection of the heart which occurs rarely in Hypertrophic Cardiomyopathy. Bacteria in the bloodstream can stick to the inside of the heart where it has been roughened by turbulent blood flow. **As uncommon as this is, the Founder of the HCMA fell victim to this. The HCMA advises extreme caution when undergoing any "invasive" medical procedure**

Heart Block

The normal electrical signal may travel down to the ventricles slowly or may even be completely blocked, "heart block". If this occurs, a pacemaker is implanted (see "other forms of therapy").

Sudden Death

Overall, in patients with Hypertrophic Cardiomyopathy there is an increased risk of premature death, which can occur with little or no warning. Sudden death can strike at any age. In the past the risk of sudden death was thought to be much higher than we believe it to be today. It is estimated that the risk of sudden death is between 1 and 2 % in the HCM population. There are members of the HCM population at a higher risk for sudden cardiac arrest, SCA, or sudden cardiac death, SCD and for those at higher risk it is advised they consult with their health care provider about receiving an implantable defibrillator.

Heart Failure

Fluid Congestion: if the heart becomes less efficient as a pump, the body will try to compensate for it. One way it attempts to do this is by using hormones and nerve signals to increase blood volume (by water retention in the kidneys). A drop in blood flow to the kidneys will also lead to fluid retention. Blood and fluid pressure backed up behind the heart result in excess salt water entering the lungs and other body tissues. However, it is important to note that not all swelling due to fluid retention is a reflection of heart failure. Clinical symptoms due to fluid congestion: shortness of breath and edema (pooling of fluid in lungs and body)

Reduced Blood Flow to the Body: The heart's inability to pump blood to the muscles and organs isn't always apparent in early stages of heart failure. Often times, it is unmasked only during increases in physical activity. In advanced heart failure, many tissues and organs may not even receive the oxygen they require for functioning at rest. Clinical symptoms due to poor blood flow to the body: difficulty exercising, fatigue and dizziness (due to low blood pressure)

“Burnt out” or “End Stage” HCM

The terms associated with this part of the HCM disease process are misleading and rather depressing. It is our goal to help readers gain a better understand this rare but important potential consequence of HCM, occurring in approximately 3% of the total HCM population. It is poorly understood at this time why this occurs. Some theories suggest it is the individual genetic mutation that determines the progression of the disease.

While “End stage”/”Burnt out” is not precisely the same it is remarkably similar to the dilated form of cardiomyopathy. In dilated cardiomyopathy (often referred to as congestive cardiomyopathy), the heart reaches a point of generalized weakening and thinning of the muscle walls with dilated chambers, particularly the left ventricle. While the walls may have previously been normal or thickened from overwork through trying to compensate for an inadequate ability to pump, (or in the case of HCM), previously “thick” muscle now changes to a different form of damaged tissue. The dilation and thinning of the cardiac chambers, especially of the left ventricle, is often referred to as “remodeling”. The weakening and dilation of the heart muscle eventually leads to heart failure. previously normal or in the case of HCM, previously “thick” heart muscle changes to a different form of damaged tissue, leading to a generalized weakening of the walls of the cardiac chambers. To compensate for the weakening of their muscular walls, the cardiac chambers dilate. (The dilation of the cardiac chambers, especially of the left ventricle, is often referred to as "remodeling.") The weakening and the dilation of the heart muscle eventually leads to heart failure.